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Link prediction in multiplex online social networks
Mahdi Jalili, Yasin Orouskhani, Milad Asgari, Nazanin Alipourfard, Matjaž Perc, 2017, izvirni znanstveni članek

Opis: Online social networks play a major role in modern societies, and they have shaped the way social relationships evolve. Link prediction in social networks has many potential applications such as recommending new items to users, friendship suggestion and discovering spurious connections. Many real social networks evolve the connections in multiple layers (e.g. multiple social networking platforms). In this article, we study the link prediction problem in multiplex networks. As an example, we consider a multiplex network of Twitter (as a microblogging service) and Foursquare (as a location-based social network). We consider social networks of the same users in these two platforms and develop a meta-path-based algorithm for predicting the links. The connectivity information of the two layers is used to predict the links in Foursquare network. Three classical classifiers (naive Bayes, support vector machines (SVM) and K-nearest neighbour) are used for the classification task. Although the networks are not highly correlated in the layers, our experiments show that including the cross-layer information significantly improves the prediction performance. The SVM classifier results in the best performance with an average accuracy of 89%.
Ključne besede: social networks, complex networks, signed networks, link prediction, machine learning
Objavljeno: 08.08.2017; Ogledov: 56; Prenosov: 1
.pdf Polno besedilo (940,17 KB)

Morphological evolution of the skull in closely related bandicoot rats
Boris Kryštufek, Franc Janžekovič, Rainer Hutterer, Tina Klenovšek, 2016, izvirni znanstveni članek

Opis: We addressed the effects of phylogeny, ecology, and allometry on shape variation in ventral cranium, mandible and maxillary tooth-row in all five extant bandicoot rats. These rats are classified into two genera (Bandicota and Nesokia) and occupy different ecological niches along fossorial to aquatic gradient. The analysed structures are controlled by different gene loci, have diverse developmental patterns and different functional roles what induced us to hypothesize that they respond differently to the interplay between phylogenetic constrains and selective pressures. This was indeed the case in our results. Ventral cranial shape contained an apparent phylogenetic signal at various levels of taxonomic hierarchy of bandicoot rats and therefore accurately replicated the taxonomic hierarchy within the group. Molar crowns, which are less rich in anatomical complexity than the ventral cranium, provided a taxonomic grouping that was less straightforward in comparison with the skull. The phylogenetic signal was diluted in the mandible, probably by adaptive trends for the ecological niche. Unsurprisingly, an ecological gradient from a fossorial to aquatic ecotype explained 19.1% of mandibular shape variation. The major differences between ecotypes were on mandibular landmarks associated with insertion of major muscles that move the mandible during chisel-tooth drilling in fossorial B. bengalensis and N. indica. Among the three structures, the mandible was also the most affected by allometry, with size accounting for 14.0% of shape variability. Nesokia and Bandicota are by far the youngest murine taxa still attributed to a generic level. Small genetic differences however sharply contrast with unique shape features, evident in craniodental structures of these rats. This is particularly relevant for the endangered N. bunnii which is only known from a small range and peripheral isolate in Iraq. Morphological uniqueness emphasizes its ‘value’ in conservation policies more accurately than genetic metrics, making it more “visible” in a bunch of pest rats.
Ključne besede: fossorial ecotype, mandible, molars, phenotypic plasticity, phylogenetic structuring
Objavljeno: 07.08.2017; Ogledov: 26; Prenosov: 1
.pdf Polno besedilo (7,18 MB)

Computation of focus quantities of three-dimensional polynomial systems
Valery Romanovski, Douglas Shafer, 2014, izvirni znanstveni članek

Opis: Fix a collection of polynomial vector fields on $R^3$ with a singularity at the origin, for every one of which the linear part at the origin has two pure imaginary and one non-zero eigenvalue. Some such systems admit a local analytic first integral, which then defines a local center manifold of the system.Conditions for existence of a first integral are given by the vanishing certain polynomial or rational functions in the coefficients of the system called focus quantities. In this paper we prove that the focus quantities have a structure analogous to that in the two-dimensional case and use it to formulate an efficient algorithm for computing them.
Ključne besede: integrability, focus quantities, center conditions
Objavljeno: 07.08.2017; Ogledov: 37; Prenosov: 0
.pdf Polno besedilo (486,16 KB)

New data on distribution of the European pond turtle Emys orbicularis (Linnaeus, 1758) in the Podravje region (NE Slovenia)
Marijan Govedič, Milan Vogrin, Dejan Bordjan, Dominik Bombek, Damijan Denac, Tatjana Gregorc, Franc Janžekovič, Nino Kirbiš, Melita Vamberger, 2016, kratki znanstveni prispevek

Opis: Ten new observations of the European pond turtle Emys orbicularis (Linnaeus, 1758) in the Podravje region are presented. One observation is fairly old, while the others have been made in the last six years. Most of the data are just random observations and do not give a complete overview of the species distribution in the Podravje region. New data suggest that the European pond turtle is more abundant in the Drava River basin than previously known. Distribution and population size of the species in the Drava River basin still remain to be investigated in detail and not only at the Natura 2000 Drava site, especially in the areas of potential habitats prior to planning any new activities.
Ključne besede: European pond turtle, Emys orbicularis, Drava river, Podravje, Slovenia
Objavljeno: 07.08.2017; Ogledov: 33; Prenosov: 1
.pdf Polno besedilo (363,19 KB)

Duality of terrestrial subterranean fauna
Tone Novak, Matjaž Perc, Saška Lipovšek Delakorda, Franc Janžekovič, 2012, izvirni znanstveni članek

Opis: Terrestrial animals in subterranean habitats are often classified according to their degree of morphological or ecological specialization to the subterranean environment. The commonly held view is that, as distance into a cave increases, the frequency of morphologically specialized, i.e., troglomorphic, species or ecological specialization will increase. We tested this hypothesis for the fauna in 54 caves in Slovenia-the classical land for subterranean biology. We found that there exist two ecologically well separated terrestrial subsurface faunas: one shallow and one deep. 1) The shallow subterranean fauna, adapted to the terrestrial shallow subterranean habitats (SSHs) in the upper 10 m of subsurface strata, is most diverse. It consists of randomly distributed non-troglobionts and a major group of troglobionts adapted to the soil root zone. 2) The deep subterranean fauna is represented by a minor group of troglobionts, adapted to caves. Troglobionts are strictly divided between the two faunas. There is strong evidence that in karstic ecosystems with deep-rooted vegetation this might be a global pattern, or that in these locations only the shallow subterranean fauna exist.
Ključne besede: endemites, superficial subterranean habitats, trogloxenes, troglophiles, troglobionts
Objavljeno: 04.08.2017; Ogledov: 53; Prenosov: 0
.pdf Polno besedilo (1,94 MB)

Cold tolerance in terrestrial invertebrates inhabiting subterranean habitats
Tone Novak, Nina Šajna, Estera Antolinc, Saška Lipovšek Delakorda, Dušan Devetak, Franc Janžekovič, 2014, izvirni znanstveni članek

Opis: Most organisms are able to survive shorter or longer exposure to sub-zero temperatures. Hypothetically, trogloxenes characterized as not adapted, and troglophiles as not completely adapted to thermally stable subterranean environment, have retained or partially retained their ability to withstand freezing, while most troglobionts have not. We tested this hypothesis experimentally on 37 species inhabiting caves in Slovenia, analyzing their lower lethal temperatures in summer and winter, or for one season, if the species was not present in caves during both seasons. Specimens were exposed for 12 hrs to 1°C-stepwise descending temperatures with 48 hr breaks. In general, the resistance to freezing was in agreement with the hypothesis, decreasing from trogloxenes over troglophiles to troglobionts. However, weak resistance was preserved in nearly all troglobionts, which responded in two ways. One group, withstanding freezing to a limited degree, and increasing freezing tolerance in winter, belong to the troglobionts inhabiting the superficial subterranean habitats. The other group, which equally withstand freezing in summer and winter, inhabit deep subterranean or other thermally buffered subterranean habitats. Data on cold resistance can thus serve as an efficient additional measure of adaptation to particular hypogean environments.
Ključne besede: endemites, superficial subterranean habitats, trogloxenes, troglophiles, troglobionts
Objavljeno: 04.08.2017; Ogledov: 27; Prenosov: 1
.pdf Polno besedilo (358,59 KB)

Vesiculation of biological membrane driven by curvature induced frustrations in membrane orientational ordering
Dalija Povše Jesenek, Šárka Perutková, Wojciech Góźdź, Veronika Kralj-Iglič, Aleš Iglič, Samo Kralj, 2013, izvirni znanstveni članek

Opis: Membrane budding often leads to the formation and release of microvesicles. The latter might play an important role in long distance cell-to-cell communication, owing to their ability to move with body fluids. Several mechanisms exist which might trigger the pinching off of globular buds from the parent membrane (vesiculation). In this paper, we consider the theoretical impacts of topological defects (frustrations) on this process in the membranes that exhibit global in-plane orientational order. A Landau–de Gennes theoretical approach is used in terms of tensor orientational order parameters. The impact of membrane shapes on position and the number of defects is analyzed. In studied cases, only defects with winding numbers m = ±1/2 appear, where we refer to the number of defects with m = 1/2 as defects, and with m = –1/2 as anti-defects. It is demonstrated that defects are attracted to regions with maximal positive Gaussian curvature, K. On the contrary, anti-defects are attracted to membrane regions exhibiting minimal negative values of K. We show on membrane structures exhibiting spherical topology that the coexistence of regions with K > 0 and K < 0 might trigger formation of defect–anti-defect pairs for strong enough local membrane curvatures. Critical conditions for triggering pairs are determined in several demonstrative cases. Then the additionally appeared anti-defects are assembled at the membrane neck, where K < 0. Consequent strong local fluctuations of membrane constituent anisotropic molecules might trigger membrane fission neck rupture, enabling a membrane fission process and the release of membrane daughter microvesicles (ie, vesiculation).
Ključne besede: structural transitions, topological defects, membrane microvesicles, membrane curvature, membrane fission, vesiculation
Objavljeno: 03.08.2017; Ogledov: 26; Prenosov: 0
.pdf Polno besedilo (4,92 MB)

Towards contemporary neuroethics
Niko Gorjup, Rado Gorjup, 2014, izvirni znanstveni članek

Opis: The main message we are trying to get across throughout the article is that the placebo is not an inert entity but instead it has a potential of subjective interpretation, a healing potential of its own, over and above that of any healing potential of the medication per se. Such healing potential is greatly dependent on how strong the interpretation value in being healed is that is created by the doctor. In this regard, we are also arguing that there are myriads possibilities at work that can influence how strong this interpretation value can become. The crucial role of contemporary medicine should be to expand the use of these interpretation effects even more and use them to help reduce any negative mental states that could continue to suppress the immune system after the initial healing. In other words, medicine should use the power of interpretation effect not only to re-arouse the immune system temporarily but permanently. In order to achieve a complete process of permanent healing it is necessary to take advantage of making full use of the powerful interpretation value through psychosocial context. It is possible to do that beyond the usual "sugar pill" through evidence based approach - a science of compassionate care! By introducing the new operational placebo definitions, we clearly show that the human mind (unconscious and conscious) is an inevitable substance involved in the Healing Process. The terms "placebo", "placebo effect", and "placebo response" are re-defined into the new working definitions. We explain how there is no more distinction (duality) such as body / mind, specific / nonspecific or health / disease, which offers new insights for future directions in contemporary Neuroethics.
Ključne besede: placebo, bioelectromagnetics, evidence-based medicine, compassionate care, neuroethics
Objavljeno: 03.08.2017; Ogledov: 23; Prenosov: 0
.pdf Polno besedilo (183,83 KB)

Symmetry breaking and structure of a mixture of nematic liquid crystals and anisotropic nanoparticles
Marjan Krašna, Matej Cvetko, Milan Ambrožič, 2010, izvirni znanstveni članek

Opis: Orientational ordering of a homogeneous mixture of uniaxial liquid crystalline(LC) molecules and magnetic nanoparticles (NPs) is studied using the Lebwohl-Lasher lattice model. We consider cases where NPs tend to be oriented perpendicularly to LC molecules due to elastic forces. We study domain-type configurations of ensembles, which are quenched from the isotropic phase. We show that for large enough concentrations of NPs the long range uniaxial nematic ordering is replaced by short range order exhibiting strong biaxiality. This suggests that the impact of NPs on orientational ordering of LCs for appropriate concentrations of NPs is reminiscent to the influence of quenched random fields which locally enforce a biaxial ordering.
Ključne besede: liquid crystals, nanoparticles, disorder, orientational order, quenched disorder, symmetry breaking
Objavljeno: 03.08.2017; Ogledov: 30; Prenosov: 0
.pdf Polno besedilo (447,84 KB)

Inheritance patterns in citation networks reveal scientific memes
Tobias Kuhn, Matjaž Perc, Dirk Helbing, 2014, izvirni znanstveni članek

Opis: Memes are the cultural equivalent of genes that spread across human culture by means of imitation. What makes a meme and what distinguishes it from other forms of information, however, is still poorly understood. Our analysis of memes in the scientific literature reveals that they are governed by a surprisingly simple relationship between frequency of occurrence and the degree to which they propagate along the citation graph. We propose a simple formalization of this pattern and validate it with data from close to 50 million publication records from the Web of Science, PubMed Central, and the American Physical Society. Evaluations relying on human annotators, citation network randomizations, and comparisons with several alternative approaches confirm that our formula is accurate and effective, without a dependence on linguistic or ontological knowledge and without the application of arbitrary thresholds or filters.
Ključne besede: memes, inheritance, genes, network science, complex systems
Objavljeno: 03.08.2017; Ogledov: 18; Prenosov: 0
.pdf Polno besedilo (2,85 MB)

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